1. Field of the Invention
The present invention relates to a sheet tray assembly that is to be detachably disposed in an image recording apparatus.
2. Discussion of Related Art
In an inkjet printer, recording sheets are conveyed along a sheet path by a sheet conveyor, and each of the recording sheets is subjected to a recording operation performed by an image recorder. The recording sheet is performed by a recording head of the image recorder which is activated to eject ink onto each recording sheet while the recording sheet is being conveyed. US 2007/0138193A1 (corresponding to JP-2007-160816A) discloses an inkjet printer in which a printer cover can be opened to permit a maintenance operation to be performed onto a sheet conveyor and an image recorder that are provided inside the printer. The printer cover is connected via a link to a housing of a main body of the printer. The link has holes provided in its respective opposite end portions. A first shaft provided in the housing is introduced in one of the holes of the link, while a second shaft provided in the printer cover is introduced in the other of the holes of the link. A coil spring is attached to the first shaft, and constantly forces or biases the link to be pivoted in a direction that causes the pivot cover to be opened. The printer cover is pivotable relative to the housing about the first and second shafts, i.e., two axes. When the printer cover is raised by a user, the printer cover and the link are pivoted integrally with each other relative to the main body of the printer. When the link has been pivoted to a predetermined position, the link is brought into contact at its protruding portion with the housing. In this state, the pivot movement of the link is stopped by the contact of the link with the housing. From this state, the printer cover is pivoted relative to the link as well as the main body of the printer. An opening of the main body of the printer is thus exposed.
Some of image recording apparatuses such as inkjet printers and laser printers are equipped with sheet tray assemblies such as sheet-supplying cassettes. The sheet tray assembly is provided for accommodating recording sheets each of which is to be subjected to an image recording operation, and is detachably disposed in the image recording apparatus. The sheet tray assembly has a tray unit and a cover unit. The tray unit has an upper opening for allowing the recording sheets to be introduced into the tray unit via the upper opening. The cover unit is disposed on an upper side of the tray unit to cover a rear side region of the upper opening of the tray unit, and is pivotable relative to the tray unit about a pivot axis. A front side region of the upper opening of the tray unit is uncovered, because a pickup roller is disposed in the front side region of the upper opening so as to be held in pressing contact with the recording sheets accommodated in the tray unit. The pivot axis is located in the upper opening of the tray unit. When the cover unit is opened, the rear side region of the upper opening of the tray unit is uncovered, and the recording sheets can be accommodated in the tray unit by introducing leading ends of the respective recording sheets into the tray unit via a space defined on a lower side of the pivot axis.
In the above-described conventional sheet tray assembly, since the pivot axis (about which the cover unit is pivotable) is located in the upper opening of the tray unit, a proximal end portion of the cover unit which is in the vicinity of the pivot axis enters into the tray unit when the cover unit is opened. Therefore, the above-described space defined on the lower side of the pivot axis is reduced when the cover unit is opened, thereby causing a problem that only a limited number of sheets (e.g., recording sheets) can be introduced into the tray unit via the recued space, namely, only a limited number of sheets can be accommodated in the tray unit. In other words, there is a problem that the entrance of the proximal end portion of the cover unit into the tray unit causes a dead space within the tray unit wherein the dead space is not available for accommodation of the sheets. It might be possible to solve the problem, for example, by heightening a position of the pivot axis. However, heightening the position of the pivot axis causes another problem that the image recording apparatus as a whole is increased in size. Anyway, it has been difficult to utilize an entirety of inner space of the sheet tray assembly as a space available for accommodating therein the sheets.